The present invention relates to an oil production method for producing oil at high recovery factor from oil-containing reservoirs by providing horizontal wells comprising at least a gas injection well and a production well, which are disposed horizontally opposing to each other.
It is described that improvement can be obtained in productivity of oil through the horizontal well rather than the vertical one, among various oil producing methods, for example, in xe2x80x9c7th Abu Dhabi International Petroleum Exhibition and Conference (ADIPEC) Oct. 13-16, 1996, Abu Dhabi-U.A.E., xe2x80x9cProceedingsxe2x80x9d pp. 791-801, SPEC#36247, xe2x80x9cImproved Oil Recovery By Pattern Gas Injection Using Horizontal Wells in a Tight Carbonated Reservoirxe2x80x9d.
However, in the conventional art mentioned above, any consideration was not paid to optimization of the distance, etc., between the gas injection well and the production well in the horizontal wells to be drilled or excavated.
An object, according to the present invention, is to provide an oil production method, wherein oil can be produced from oil-containing reservoirs at a high recovery factor, by optimizing the distance between the gas injection well and the production well in the horizontal wells to be drilled with respect to a certain oil-containing reservoir.
For accomplishing the above-mentioned object, according to the present invention, there is provided a method for producing oil from an oil-containing reservoir using horizontal wells, which are drilled into the oil-containing reservoir, at an appropriate distance between a gas injection well and a production well thereof, depending upon at least a ratio between an averaged vertical permeability and an averaged horizontal permeability (a ratio kv/kh) in the oil-containing reservoir producing the oil therefrom.
Also, according to the present invention, there is provided a method for producing oil from an oil-containing reservoir using horizontal wells, which are drilled into the oil-containing reservoir with an appropriate distance between a gas injection well and a production well thereof, the distance depending upon at least a ratio between an averaged vertical permeability and an averaged horizontal permeability (a ratio kv/kh), layer thickness and inclination of the oil-containing reservoir producing the oil therefrom.
Also, according to the present invention, there is provided a method for producing oil from an oil-containing reservoir using horizontal wells, which are drilled into the oil-containing reservoir with appropriate distance between a gas injection well and a production well thereof, the distance depending upon at least a ratio between an averaged vertical permeability and an averaged horizontal permeability, layer thickness and inclination of the oil-containing reservoir producing the oil therefrom, and compositions of a gas to be injected as well.
Also, according to the present invention, in the method for producing oil as defined above, the ratio between an averaged vertical permeability and an averaged horizontal permeability (a ratio kv/kh) is calculated up on a basis of a result of a core analysis or a spot test (including a special well test) in the oil-containing reservoir.
Also, according to the present invention, there is provided a method for producing oil from an oil-containing reservoir, comprising a sequence of the following steps:
a first calculation step for calculating a ratio between an averaged vertical permeability and an averaged horizontal permeability, a layer thickness and an inclination, upon a basis of a result of a core analysis or spot test on the oil-containing reservoir producing the oil therefrom;
a second calculation step for calculating an appropriate distance between a gas injection well and a production well, through conducting simulation upon a relationship between viscous force and buoyancy using a model of horizontal wells on said oil-containing reservoir, from the averaged vertical permeability and the averaged horizontal permeability, the layer thickness and the inclination, which are assumed in said first calculation step;
a step for drilling the horizontal wells including the gas injection well and the production well, so that they are kept at the calculated appropriate distance between them, which is calculated out in said second calculation step; and
a step for producing the oil from the oil-containing reservoir using the horizontal wells drilled in said drilling step.